This invention relates to the synthesis of unsymmetrical cyclotetraenes and to novel 8-membered ring heterocyclic compounds produced thereby. More particularly, this invention concerns itself with a novel method for synthesizing 1,3-diphospha-2,4,6,8-tetraazacyclooctatetraens. The resulting compounds find application as antioxidant and anticorrosive additives for perfluorinated-based lubricating fluids and greases as well as other applications requiring the use of antioxidant agents.
The present interest in the utilization of perfluoroalkylether type fluids for high temperature lubicating applications has created a need for effective antioxidant and anticorrosive additives. Although the perfluorinated fluids possess excellent thermal and oxidative characteristics, their potential is somewhat limited due to their tendency to corrode certain metals present in aircraft components. This constitutes a serious drawback in their use as a lubricant since the corroding metal in turn degrades the perfluorinated fluid. This phenomenon tends to occur at temperatures above 550.degree. F. in an oxidative environment.
The need for effective additives to counter the corrosive effect of the perfluorinated fluids on metal parts becomes quite obvious. As a result, a considerable research effort has been undertaken in an attempt to provide new additives which would overcome the corrosion problems encountered when using perfluorinated lubricants in certain high temperature applications within an oxidative environment.
As a result of the concerted research effort referred to above, it has been found that unsymmetrical diphosphatetraazacyclooctatetraenes can be obtained by effecting a reaction between a perfluoroalkylether imidoylamidine and an imido-tetraaryl-diphosphinic acid trichloride. The resulting 8-membered ring compounds are excellent additives for use in perfluorinated lubricants and overcome the corrosion problem associated with the use of these lubricants in high temperature, aerospace applications.